commit https://github.com/vim/vim/commit/6fc8227ebfbdfbbb48b81b679db81f421dbce79b Author: Bram Moolenaar <Bram@vim.org> Date: Sun Aug 28 19:26:43 2016 +0200 patch 7.4.2287 Problem: The callback passed to ch_sendraw() is not used. Solution: Pass the read part, not the send part. (haya14busa, closes https://github.com/vim/vim/issues/1019)

--- a/src/channel.c
+++ b/src/channel.c
@@ -3456,7 +3456,7 @@ send_common(
 	    EMSG2(_("E917: Cannot use a callback with %s()"), fun);
 	    return NULL;
 	}
-	channel_set_req_callback(channel, part_send,
+	channel_set_req_callback(channel, *part_read,
 				       opt->jo_callback, opt->jo_partial, id);
     }